N-linked oligosaccharides are not involved in the function of a cell-cell binding glycoprotein E-cadherin

E-cadherin is a Ca2+-dependent cell-cell adhesion molecule identified as a glycoprotein with a molecular weight (MW) of 124,000. To study the role of the sugar moieties of this adhesion molecule, we tested the effect of tunicamycin on aggregation mediated by E-cadherin of teratocarcinoma cells. Immunoblot analysis using a monoclonal antibody to E-cadherin showed that in cells treated with tunicamycin this adhesion molecule is converted into two forms with MW of 118,000 and 131,000. The smaller one was exposed on the cell surface and showed a trypsin sensitivity characteristic to E-cadherin, suggesting that this is the peptide moiety of E-cadherin whose glycosylation with N-linked oligosaccharides was blocked by tunicamycin. The larger one was not removed by trypsin treatment of cells, suggesting an intracellular location. These tunicamycin-treated cells aggregated in a Ca2+-dependent manner, and the aggregation was inhibited by a monoclonal antibody to E-cadherin. These results suggested that N-linked oligosaccharides are not involved in the functional sites of this adhesion molecule.